A conventional playback signal processing device in an optical disk device or the like is described in Patent Document 1. An example of this type of conventional playback signal processing device is shown in FIG. 5.
In FIG. 5, 100 refers to a recording medium such as an optical disk; 101 to an optical pickup; 102 to an analog front end; 103 to an A/D converter; 104 to an interpolator; 105 to a digital equalizer; 106 to a timing recovery circuit; 107 to a synthesizer; RSD to resampled data; and RSC to a resampled clock.
To play back data written in the recording medium 100, the recording medium 100 is first irradiated with laser light, and the optical pickup 101 captures the reflected light to convert differences in the intensity of the reflected light into an electric signal, thereby generating an analog playback signal. The analog playback signal obtained by the optical pickup 101 is then subjected, in the analog front end 102, to signal amplitude gain adjustment and DC offset adjustment, and then to waveform equalization and noise removal processing.
The analog playback signal subjected to the waveform equalization processing in the analog front end 102 is quantized by the A/D converter 103 in accordance with a fixed clock output from the synthesizer 107 and thereby becomes playback data having a digital value. In the subsequent stages, digital signal processing is performed. Based on frequency ratio information output from the timing recovery circuit 106, the interpolator 104 generates the resampled data RSD and the resampled clock RSC from the playback data quantized by the A/D converter 103 and outputs the resampled data RSD and the resampled clock RSC. The digital equalizer 105 receives the resampled data RSD and the resampled clock RSC from the interpolator 104 and performs waveform correction processing on the resampled data RSD and the resampled clock RSC. The timing recovery circuit 106 receives, from the digital equalizer 105, the resampled data RSD and the resampled clock RSC subjected to the waveform correction processing, and performs clock extraction from the resampled data RSD and the resampled clock RSC to output the frequency ratio information on the ratio between a channel clock frequency contained in the analog playback signal and the resampled clock frequency.
Patent Document 1: Japanese Laid-Open Publication No. 2000-48490 (FIG. 1)